1. Field
The present invention relates to a backlight unit and a backlight driving circuit board, and a liquid crystal display (LCD) module using the backlight unit.
2. Related Art
Flat panel display (FPD) devices have a relatively light weight, thin profile, and low power consumption. FPD devices are commonly used as a substitute for cathode ray tube (CRT) devices. Generally, display devices may be classified according to self-emission. For example, display devices may be classified as emissive display devices or non-emissive display devices. Emissive display devices display images by self-emitting light. Non-emissive display devices require a light source since they do not emit light by themselves. For example, plasma display panel (PDP) devices, field emission display (FED) devices, and electroluminescent display (ELD) devices are commonly used emissive display devices. Liquid crystal display (LCD) devices may be categorized as non-emissive display devices. However, some applications of LCD devices do not require a light source. LCD devices are commonly used in notebook and desktop computers because of their high resolution, color display capability, and high quality image.
LCD devices include an LCD module. The LCD module includes an LCD panel that displays images to an exterior and a backlight unit that supplies light to the LCD panel. The LCD panel includes two substrates that face each other and are spaced apart from each other. A liquid crystal material is interposed therebetween. Liquid crystal molecules of the liquid crystal material have a dielectric constant and refractive index anisotropic characteristics due to their long thin shape. Two electric field generating electrodes are formed on the two substrates, respectively. An orientation alignment of the liquid crystal molecules may be controlled by supplying a voltage to the two electrodes such that transmittance of the LCD panel is changed according to polarization properties of the liquid crystal material.
Generally, an additional light source is required because the LCD panel is a non-emissive-type display device. Accordingly, a backlight unit is disposed under the LCD panel. The LCD device displays images using light produced by the backlight unit and supplied to the LCD panel. Backlight units may be classified into a side-type backlight unit and a direct-type backlight unit in accordance with a disposition of the light source. The direct-type backlight unit has one lamp or a couple of lamps disposed at a side portion of a light guide plate. Alternatively, at least one lamp is disposed at each side portion of the light guide plate, respectively.
The side-type backlight unit has a plurality of lamps disposed under the light guide plate. In a large sized LCD module, the direct-type backlight unit may provide the LCD module with a uniform light source although the side-type backlight unit is more easily manufactured than the direct-type.
FIG. 1 is a schematic perspective view showing a direct-type backlight unit according to the related art. As shown in FIG. 1, a direct-type backlight unit includes a bottom frame 50, a reflective sheet 22 on the bottom frame 50, and a plurality of fluorescent lamps 24 on the reflective sheet 22. Both sides of the bottom frame 50 are bent toward an inner portion thereof. Although not shown, the reflective sheet 22 has a plurality of holes corresponding to the plurality of fluorescent lamps 24, so the light from the fluorescent lamp 24 is substantially exposed through the hole. For example, the reflective sheet 22 covers an inner surface of the bottom frame 50 except for the area where the fluorescent lamps 24 are disposed. Although not shown, a diffusion plate and an optical sheet group may be disposed on the fluorescent lamp.
As shown in FIG. 1, the fluorescent lamps are arranged parallel to each other and are driven by a high-low type that has a ground portion formed at respective end portions of the fluorescent lamps 24. Light from the fluorescent lamp 24 is emitted by applying an alternating current voltage waveform through a wire 36 that extends from an electrode (not show) in the fluorescent lamp 24.
As shown in FIG. 1, the fluorescent lamp 24 includes at least two fluorescent lamps. The couple of fluorescent lamps are fixed on the bottom frame 50 with a lamp holder 32 connected with the wire 35 that is connected to an external power supply. The wire 36 extends from a backside of the bottom frame 50 and is connected to a socket connector 38a at an end portion of the wire 36.
An inverter 40 that converts a direct current voltage into an alternating current voltage is necessary because the alternating current voltage is required to drive the fluorescent lamp 24. A backlight driving circuit board 34, which includes a driving circuit (not shown) of the fluorescent lamp 24 and the inverter 40, is mounted on the backside of the bottom frame 50. The backlight driving circuit 34 further includes a plug connector 38b that connects the socket connector 38a and the backlight driving circuit 34. A power supply is applied to the fluorescent lamp 24 through connecting the socket connector 38a and the plug connector 38b. 
The wire 36 is exposed at the backside of the bottom frame 50, as shown in FIG. 2, for example, when the backlight driving circuit board 34 is mounted on the backside of the bottom frame 50 and when the socket connector 38a, which is connected to the end portion of the wire 36 that extends from the fluorescent lamp 24, is connected to the plug connector 38b on the backlight driving circuit board 34.
Accordingly, the exposed wires 36 may contact each other, which would create a short or interference between the wires 36 and leakage of the voltage may occur by the alternating current voltage applied to the respective wires 36. Consequently, there is a problem that the emission of the fluorescent lamp 24 is not uniform.